The present invention relates to a clutch arrangement for use in an automotive driveline and particularly to an apparatus for controlling an automatically operated clutch assembly for use with a manually operated power transmission system of an automotive vehicle.
An automatically operated clutch assembly for automotive use is usually of a dry-disc friction type and difficulties have been encountered in putting such a clutch assembly to practical use primarily for the following reasons. One reason is that the pressure exerted between the driving and driven members of the clutch assembly can not be controlled accurately during a partially coupled condition of the clutch assembly when the driving and driven members tend to slide on each other. Another reason is that the engine is restrained from delivering an output speed to match the position of the accelerator pedal when the driveline posterior to the clutch assembly is subjected to an increased load. When, furthermore, the clutch assembly is actuated repeatedly at short intervals, the temperature of the clutch disc is increased excessively and causes reduction of the friction of the clutch facings. This adds to the tendency of the driving and driven members of the clutch assembly to slide on each other and causes the engine to operate in an unloaded condition producing an extremely high output speed.
To avoid these problems, attempts have been made to provide an automatic clutch arrangement using a combination of a torque converter or a magnetic-particle or centrifugal clutch assembly for the purpose of starting the vehicle from a halt and a dry-disc friction clutch for the shifting of gear positions in the transmission system. The clutch arrangement of this nature is controlled in dependence upon each individual clutch assembly and, for this reason, not only expensive control devices are required but there is a tendency that the manipulative efforts of the vehicle operator are ineffective. If, furthermore, a torque converter is utilized for the starting of the vehicle, the fuel consumption rate of the engine becomes far higher than in a vehicle using a manually operated clutch arrangement due to the sliding tendency between the driving and driven members of the torque converter. Such a drawback is also involved in a fluid-operated fully automated power transmission system.